As you rightly say, writing and speaking are about communicating and language is always in flux. Statistically we can identify those things that break communication versus those things that simply impede it. As English lacks the structure of a synthetic language like Russian, word order is essential. But beyond that, clarity comes from vocabulary (phrasal verbs are notoriously ambiguous) and precision (pronouns often lead to confusion). "He said he was going to tell him to say to him that he shouldn't count on lucking out but he should throw down and make out the reaction" is mostly incomprehensible. People should focus less on false rules (the split infinitive) and more on basic clarity. At least, if we want to be comprehensible to others in terms of nominal content rather than in terms of in-group signaling.